The present invention relates generally to ablation devices and, more specifically, to an assembly of ablation elements arranged in a staggered configuration.
Hypertension is a major global public health concern. An estimated 30-40% of the adult population in the developed world suffers from this condition. Furthermore, its prevalence is expected to increase, especially in developing countries. Diagnosis and treatment of hypertension remain suboptimal, even in developed countries. Despite the availability of numerous safe and effective pharmacological therapies, including fixed-drug combinations, the percentage of patients achieving adequate blood-pressure control to guideline target values remains low. Much failure of the pharmacological strategy to attain adequate blood-pressure control is attributed to both physician inertia and patient non-compliance and non-adherence to a lifelong pharmacological therapy for a mainly asymptomatic disease. Thus, the development of new approaches for the management of hypertension is a priority. These considerations are especially relevant to patients with so-called resistant hypertension (i.e., those unable to achieve target blood-pressure values despite multiple drug therapies at the highest tolerated dose). Such patients are at high risk of major cardiovascular events.
Renal sympathetic efferent and afferent nerves, which lie within and immediately adjacent to the wall of the renal artery, are crucial for initiation and maintenance of systemic hypertension. Indeed, sympathetic nerve modulation as a therapeutic strategy in hypertension had been considered long before the advent of modern pharmacological therapies. Radical surgical methods for thoracic, abdominal, or pelvic sympathetic denervation had been successful in lowering blood pressure in patients with so-called malignant hypertension. However, these methods were associated with high perioperative morbidity and mortality and long-term complications, including bowel, bladder, and erectile dysfunction, in addition to severe postural hypotension. Renal denervation is the application of a chemical agent, or a surgical procedure, or the application of energy to partially or completely damage renal nerves to partially or completely block the renal nerve activities. Renal denervation reduces or completely block renal sympathetic nerve activity, increases renal blood flow (RBF), and decreases renal plasma norepinephrine (NE) content.
That renal denervation can prevent or delay hypertension was known as early as 1936. See Heuer G J. The surgical treatment of essential hypertension, Annals of Surgery, 1936; 104 (4): 771-786. The surgical denervation, i.e., sympathectomy, was applied for treatment of hypertension, though with many clinical complications. Catheter renal intervention was developed much earlier, and catheter for renal angiography was introduced in 1950. Numerous publications are available on the application of electrical energy to renal nerves and the renal responses. The earliest insight into the influence of the renal nerves on renal function is that of Claude Bernard in 1859. RF ablation has been used for tumor removal for many years and there have been a great amount of publications on pulmonary venous (PV) ablation for treating AF since 1998. Intra-blood vessel RF ablation may damage nerves as documented in patent publications in 2002. See, e.g., Acker D., WO/2002/085192, Improvement in Ablation Therapy, CIPI, Oct. 31, 2002; see also Smithwick R H, Surgical treatment of hypertension, Am J Med 1948, 4:744-759; Allen E V, Sympathectomy for essential hypertension, Circulation, 1952, 6:131-140; Smithwick R H, Thompson J E, Splanchnicectomy for essential hypertension: results in 1,266 cases, JAMA, 1953, 152:1501-1504; Morrissey D M, Brookes V S, Cooke W T, Sympathectomy in the treatment of hypertension, review of 122 cases, Lancet, 1953, 1:403-408; Whitelaw G P, Kinsey D, Smithwick R H, Factors influencing the choice of treatment in essential hypertension: surgical, medical, or a combination of both, Am J Surg, 1964, 107:220-231; Gottschalk C W, Renal nerves and sodium excretion, Ann. Rev. Physiol., 1979, 41:229-40; Mancia G., Grassi G., Giannattasio C., Seravalle G., Sympathetic activation in the pathogenesis of hypertension and progression of organ damage, Hypertension 1999, 34 (4 Pt 2): 724-728; DiBona G F, Sympathetic nervous system and the kidney in hypertension, Curr Opin Nephrol Hypertens, 2002, 11(2):197-200; Haïssaguerre M et al., “Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins,” New England Journal of Medicine, 1998, 339:659-666; Chen, S A et al., “Initiation of atrial fibrillation by ectopic beats originating from the pulmonary veins: electrophysiological characteristics, pharmacological responses, and effects of radiofrequency ablation,” Circulation, 1999, 100:1879-1886; and Shah D C, Haissaguerre M, Jais P, Catheter ablation of pulmonary vein foci for atrial fibrillation: pulmonary vein foci ablation for atrial fibrillation, Thorac Cardiovasc Surg, 1999, 47(suppl. 3):352-356. The entire disclosures of these publications are incorporate herein by reference.
The object of renal denervation is to neutralize the effect of renal sympathetic system which is involved in arterial hypertension. Device-based renal denervation may achieve such objective, but may produce possible complications of renal artery/vein stenosis. Thus, there is a need for a device that can perform renal denervation with reduced risk of renal artery/vein stenosis.